DE2531037A1 - Continuous activated sludge sewage treatment - with breakdown of soluble nitrates by bacteria in oxygen-deficient zone - Google Patents

Abstract

Raw liq. sewage is injected into a reservoir which provides a single horizontal closed llop path. The liq. circulates at a minimum speed of 0.8 ft/sec. to prevent settling out. The liq. is aerate to promote aerobic decompsn. and formation of nitrate cpds. The liq. is circulated for a distance until the liq. is substantially devoid of oxygen when it reaches again the point of raw sewage injection. The liq. containing nitrates and the raw sewage are circulated together for a second distance in which denitrification proceeds until it reaches the next point of aeration. Liq. is continuously removed for clarification at about the same rate as the rate of injection of raw sewage. A portion of the settled sludge is returned to the reservoir. The average retention time in the reservoir is 24 hrs. The second distance is at least 10% of the sum of the first and second distances. For treating sewage so that its organic contents are broken down and the nitrates so formed are further broken down into their basic elements.

Description

Method and apparatus for treating wastewater The invention relates to a method and a device for the treatment of wastewater, wherein the organic components of the wastewater are aerobically degraded and the Nitrates formed during this aerobic breakdown are broken down into their basic elements.

The active sludge process deals with the elimination of fine Components, colloids and organic compounds that remain in wastewater after the larger and heavier substances by sieving and / or separating under the action of gravity were eliminated. These remaining materials generally include carbohydrates, Cellulose and its derivatives, proteins, amines, ammonia, mineral substances as well as bacteria and protozoa that feed on these substances.

Such wastewater is subject to oxygenation in that it in the presence of oxygen or air, creating a chemical and / or biological reaction takes place. As a result of the reaction, the sewage particles form a muddy floc that settles out easily and a growth as well Propagation of living bacteria and other smaller living organisms. In this way, the muddy floc becomes effective for absorbing and oxidizing the organic substance contained in the wastewater, so that it turns into carbon dioxide, soluble products and easily precipitable products are added. Likewise will if the process is carried out for a sufficiently long time, the ammonia content of the wastewater decomposed into nitrates and hydrogen ions. The flocculation continues to increase as it settles almost all of the sub-suspended solids of the wastewater with and also a lot of solids in colloidal state. This activated sludge "is maintained or continued to operate, by giving some of the recovered sludge back to the wastewater wrd. This separation and recirculation of the activated sludge to the untreated raw wastewater for further aeration results in a continuous purification of the water content in the wastewater, so that at least 90% of the biochemical oxygen requirement (BOD = Biochemical Oxygen Demand), which removes organic matter present in untreated wastewater will. The water remaining after the activated sludge flocculation has settled can then be delivered to neighboring rivers, streams and canals. A complete Description of such an activated sludge process with an apparatus for performing it of the method is found in U.S. Patent 2,684,941, issued July 27, 1954.

However, it should be noted that this is released as purified Wastewater still soluble nitrogen components (from of decomposition of ammonia), phosphates and the like. The submission of this material in bodies of water like rivers and lakes is undesirable because there is the growth of algae and other aquatic flora, which in turn reduces the oxygen content of the water consumed and thus the receiving water is damaged. A corresponding Denitration is generally not part of the activated sludge process according to prior art Wherever attempts have been made to identify such potential To eliminate damaging factors, these were based on the use of external denitration resins, in which the activated sludge is kept in an oxygen-free environment, so that the bacteria present are able to break down the nitrates and to consume the oxygen released in the process. Such a technique / are, however time consuming, costly, take up a lot of space and are relatively ineffective because only 50 - 60% of the nitrates formed in the activated sludge process are removed. It is therefore an essential object of the invention to provide an improved wastewater treatment process to provide.

Another object of the invention is to create a new denitration technique.

This denitration technique should preferably be used in conjunction with the activated Sludge process for wastewater treatment come to use.

Another object of the invention is aerobic decomposition and denitration of wastewater in a combined, continuous process.

Finally, the invention also aims to reduce the damaging effect of the Substantially eliminate the yield of the activated sludge process.

In fact, the invention succeeds in creating a highly effective cleaning agent and to provide denitration procedures in the event of the harmful effects of the wastewater treated by the process is essentially eliminated from water bodies and with the difficulties inherent in the previously known denitration techniques essentially be overcome. It therefore belongs to the denitration stage of the vorlipnden Invention that untreated, raw wastewater of those wastewater liquid in the Reservoir is supplied, which has already been subjected to aerobic decomposition and therefore is essentially free of oxygen. The bacteria in the activated Liquid containing sludge will therefore have additional organic material Available to react with, but suffer from a lack of oxygen. Around To satisfy this lack of oxygen, they act on the dissolved in the liquid Nitrate components, and consume the oxygen that is generated during their decomposition results. Continuous operation of the process and elimination of the solid matter in this liquid leads to a final release, which is generally no more than Contains 10% of those nitrate components produced by aerobic decomposition of ammonia generated in the liquid.

There is an apparatus for carrying out the method according to the invention provided that an aeration basin with inlet and outlet as well as at least one Contains stirring device.

When designing the device, it is essential that the inlet is adequate Has a distance from the agitator, so that for the aerobic decomposition of the waste water liquid and for the elimination of their oxygen content essentially To the extent that there is enough time available. In addition, the inlet should be sufficient far from the next ventilation point to avoid significant denitration Allow the plasr liquid to ventilate again before re-venting this liquid he follows.

Method and apparatus according to the invention for achieving this Results are explained in more detail below using the drawing, for example, Although they show: FIG. 1 a flow diagram which schematically shows the route and the process stages shows which sewage passes through according to the invention; and Fig. 2, schematic Top views of typical embodiments of devices according to the invention, which 4 and 4 show the individual parts of the device and their mutual relationship.

According to FIG. 2, the embodiment shown there shows a typical one Device according to the invention, a ventilation reservoir 10 with an inlet device 12. The reservoir 10 can be divided by a partition 14 into two sections 16, 18, such as The / shown equals can, but need not, be subdivided into areas 20, 22 are in communication with one another. An Aühreinricntung 24 is located inside of the reservoir 10 generally in the region 20. The stirring device 24 is used for Aeration of the wastewater liquid by keeping the air or oxygen above it the liquid surface is knocked into the liquid while at the same time the wastewater in the reservoir 10 in motion is held without a substantial settling of the contained sludge occurs. Such stirring devices are well known to those skilled in the art and can be freely chosen in practice, depending on whether in the individual case a horizontal or vertical arrangement of the same is cheaper.

The speed of the Rüi # device, as well as its immersion depth in the sewage can also be different, depending on how it is most beneficial Ventilation is appropriate. A vertically arranged stirring device can also be used alternately simply converted into a mixer drive device, that the speed is reduced and the depth of penetration of the driving impeller is lowered.

te position of the inlet device 12 on the reservoir 10 depends primarily Line of the relative distance between the inlet device 12 and the agitator device 24 from. In this regard, it should be noted that the distance between the agitator 24 and the inlet device 12 in the flow direction should be sufficient to to allow and also to allow significant aerobic decomposition of the wastewater liquid allow aerobic decomposition to continue to a point where the oxygen content of the wastewater liquid is essentially depleted. Likewise the distance between the inlet device 12 and the agitator device 24 should be the portion of the reservoir 10 in which the denitration process takes place, be sufficient to allow a significant degree of denitration before proceeding further ventilation takes place. For the purposes of the invention it was determined that the distance between the inlet device 12 and the agitator device 24 is at least should be about 10 so of the entire way that the sewage liquid at one complete cycle between successive ventilations at of ventilator 24, i.e. at least 10 # / the sum of a) des Distance between stirring device 24 and inlet device 12 and b) the distance between the inlet device 12 and the stirring device 24, both in each case in Direction of flow of the liquid measured.

While the position of the inlet device 12 relative to the outlet device 26 is of little impact, the inlet device 12 is preferably on attached to a point that is not immediately in front of or adjacent to the outlet device 26 is to a short-circuiting procedure as a result of the delivery of untreated Avoid wastewater liquid. Virtually every other location on the reservoir 10 is needb ## r, provided that the spacing requirements given above between inlet device 12 and stirring device 24 are fulfilled.

The connection area 22 can, if desired, be provided with a guide vane 28 to control the direction and uniformity of the flow be.

The outlet device 26 at or below the surface of the circulating Wastewater fluid leads to a sedimentation system 30. The sedimentation system 30 can contain primary and secondary sedimentation tanks as well as separation or Clarifying devices and / or additional devices for thickening the sludge and the like. The activated sludge of the sewage is in the sedimentation system 30 through Gravity settled while the clear purified water over the outlet edges of the system 30 flows out and directly to a neighboring body of water, river or Like. Can be delivered or in a secondary sedimentation tank (not shown) can be further chemically treated, clarified and sterilized The suspended Mud settling on the bottom of the System 30 drops, can completely can be deducted or it can be deducted in whole or in part, through a Line 34 can be recirculated and returned to reservoir 10 for mixing with the wastewater liquid contained therein. excess sludge overflows a gutter 32 to a sludge compactor 36 and is thereafter disposed of.

If the process steps shown in FIG. 1 are applied to the device according to Fig. 2 in relation, it can be seen that raw, untreated wastewater liquid, i.e. the mixture of wastewater and water after removal of heavier constituents remains from the wastewater into the aeration reservoir 10 0 via the inlet device 12 is introduced.

The sewage liquid is moved horizontally in the reservoir set and then brought into contact with the agitator 24, whereby it aerates and is passed further horizontally through the reservoir. The one that takes place afterwards Aerobic decomposition involves the decomposition of the organic components of the wastewater into soluble and precipitable solids, water and carbon dioxide gas. That aspect this method is used to provide a primary energy source for additional Bacterial growth. Another bacterial process leads to the conversion of the ammonia content into nitrates, which remain in the liquid as dissolved nitrogen compounds.

It should be noted that the bacteria used for the above process are used to Adhering to the sludge flocculation, which is made up of essentially all solid particles, which are suspended in the liquid is formed. In the sedimentation system 30, the flocculation settles as sludge, which when it is pumped back into the reservoir 10 bacteria with an average age of 30 to 40 days.

Aerobic decomposition is allowed to continue to a point where the oxygen content in the aerated sewage liquid is essentially depleted is. At this point 12, new, untreated sewage fluid is in motion The sewage liquid located is supplied to the Denitrierongsvorgang to go set. The conditions in the container at the point of adding new wastewater liquid, namely, the presence of additional organic matter in a substantial absence of oxygen, are ideal for keeping the bacteria in the aerated sewage liquid their oxygen requirement by decomposing the nitrogen components in the liquid to satisfy. The generated oxygen is consumed by the bacterial genes in order to keep the aerobic To cause decomposition of the newly supplied wastewater. It should be noted here that the Denitration is particularly effective when you keep the water temperature above about 50C holds.

The cycle of aerobic decomposition and denitration becomes continuous continued, with each cycle taking some reduction in the amount of organic Mat ~ ie, a partial conversion of ammonia into nitrate in the oxygen-rich range of the reservoir as well as a partial elimination of nitrate in the oxygen-poor area of the reservoir takes place.

The average residence time of the wastewater liquid in the reservoir is determined by its volume and the flow rate at which the new waste water liquid flows is supplied to the reservoir and withdrawn from the reservoir. The decomposition and the nitration is essentially achieved after a residence time of about 24 hours, although longer and shorter residence times are determined by the person skilled in the art in the individual case can be used. E.g. for a flow capacity of 24 Hours designed reservoir of admission additional Sewage the discharge of treated wastewater results in an average of 24 hours Has.

During this period, the wastewater can become 50 to 100 cycles more aerobic Decomposition and denitration go through before dispensing. Further the volume and rate of wastewater liquid discharge will generally correspond to the volume and correspond to the rate of supply of new sewage liquid.

It should be noted here that from the liquid dispensed in general at least 90% of the nitrate concentration is removed by aerobic decomposition was generated by ammonia in the liquid. While every time, there are new sewage liquid is subjected to ventilation, additional nitrate formation takes place yet the fact that the amount of newly supplied sewage liquid is small Compared to the total amount that is in the reservoir, that is the nitrate content of the liquid dispensed is not about 10% of that originally in the liquid generated nitrate content.

An additional advantage of the method according to the invention is therein to see that the decrease in pH levels, which is normally associated with denitration occurs, not present here because of the absence of nitric acid is.

Correspondingly, the formation of soluble KalzaH1 ~ t ~ phosphate complexes, which occurs at an acidic pH level, kept to a minimum in the method according to the invention, which is why there are larger amounts of phosphate in the sludge than in the released one Liquid. Such a distribution of the phosphate is ## desirable because of the lack of it of phosphates significantly reduces the environmentally damaging effects of the released liquids belittles.

It can therefore contain more phosphates and colloidal solid particles in one Follow-up procedures can be eliminated by adding iron salts, chlorides and other flocculants, preferably in a second sedimentation system, without any constituents of the secondary sludge circulating back to the reservoir will.

A variant of the device according to FIG. 2 is shown in FIG. the The embodiment of FIG. 3 corresponds to that of FIG. 2, but is in the connecting area 22 a mixing and drive device 38 is provided; this device 38 is used for niche the newly added wastewater liquid already the reservoir 10 flowing through liquid and also the liquid without significant settling of mud in motion, but it does not aerate the liquid. Insofar as the device 38 does not represent an additional ventilation device, are the relative distances between the inlet device 12 and the agitator device 24 with those described with reference to FIG. 2 in accordance.

It should be noted, however, that the mixing and driving device 38 can be replaced by a second stirring device corresponding to the stirring device 24 can, whereby a device with two agitators 24 and 38 and one Inlet device 12 results. As a result, the wastewater passes through two areas aerobic decomposition and an area with denitration circulation in the reservoir 10. At When introducing additional ventilation, it is essential that the distance between the second ventilation point 38 and the inlet device 12 is sufficient is for substantial decomposition and oxygen depletion of the waste water liquid, while the distance between the inlet device 12 and the stirring device 24 should be sufficient for adequate denitration of the wastewater, i.e. at least about 10 G5 of the distance between the agitator 38 and the Stirring device should be 24. Furthermore, either or both of these stirring devices can be convertible units that alternate as mixing and driving devices and as ventilation devices work in accordance with the requirements of the practice Individual case.

Another embodiment of the device of the invention is shown in FIG Fig. 4 shown. This device includes a reservoir 40, sections 44 and 46, which are in communication in areas 48 and 50, delimiting partition 42, a Outlet device 60 and a sedimentation system 62 with a sludge return line 64 and a channel 66 for excess sludge. The main feature of this embodiment is that the device shown in FIG. 4 has two inlet devices 52 and 54 and two agitators 56 and 58 which are so arranged relative to one another are that the dimensional relationships set out above exist. Such is the distance between the stirring device 56 and the inlet device 54 on the one hand and the Distance between the stirring device 58 and the inlet device 52 is sufficient for a substantial aerobic decomposition of the wastewater, as well as for an extensive one Depletion of its oxygen content. Likewise is the distance between the Inlet device 54 and the agitator device 58 and the distance between the inlet device 52 and the stirring device 56, always seen in the direction of flow, sufficient for substantial denitration of the sewage liquid before the next aeration takes place, the latter distances being at least about 10% of the distance between the two directions of stirring 56 and 58 amount.

With reference to the embodiment of FIG. 4, the method exists according to the invention of two aerobic decomposition and denitration cycles, per cycle the sewage liquid.

This allows the sewage to enter the inlet device 54 through the agitator 58 is set in motion and aerated, an aerobic decomposition and oxygen pulp in the area between the agitator 58 and the inlet device 52, with new wastewater supplied at the inlet device-52 mixed and in the area between the inlet device 52 and the stirring device 56 are denitrated, further aerated at the agitator 56 and further aerobic Decomposition between agitator 56 and inlet 54 exposed and then mixed again with new wastewater supplied at the inlet device 54 and subjected to further denitration; this cycle then becomes more continuous Base continued. The wastewater treated in this way is then discharged to a suitable one Time for the whole process.

Further modifications of the above-described embodiments of the inventive Devices are of course possible.

For example, a reservoir without a partition can be used for a single pass can be used in place of the preferred embodiment with divider. Likewise can either be a reservoir with multiple subdivisions or a plurality of aeration reservoirs connected in series can be used instead of one individual reservoirs divided into two lanes by a partition wall according to the one shown Embodiments.

The ventilation reservoir can be connected to any number of niche and drive devices be equipped, which can be mounted in different places in the reservoir, as well as any number of inlet and outlet devices, whereby all that is required is the necessary clearances for aerobic decomposition and denitration to be observed. Furthermore, the inlet device can be arranged so that it can still untreated wastewater liquid in the direction of flow the aerated sewage liquid supplies. That way it gets the movement increased propulsion of the liquid in the reservoir.

On the other hand, addition in one of the circulation lines has the opposite effect Direction of a more rapid mixing of the incoming new wastewater with the circulating Liquid.

Guide vanes can be found in the reservoir near the agitator and / or are provided in the connecting area of the divided sections in order to to increase the aeration of the sewage fluid and its movement and orientation to support.

In addition, the reservoir can be equipped with heating devices and / or insulating Covers are provided to speed up the process or to provide a suitable one Maintain speed when working at low temperatures.

The method according to the invention will be based on a specific one below Implementation example explained, using the device according to FIG. 3 and Wastewater liquid was filled into a reservoir, which is a single one in itself closed horizontal flow path 750 feet (about 230 m) in length was provided with stirring and drive devices such that the movement of the liquid at a minimum speed of 0.8-1.0 feet / sec (approximately 0.25-0.30 m / sec) The ventilation device releases air at a rate of about 2 - Beat 4 libs (about 0.9-1.8 kg) oxygen / h into the wastewater.

It was found that the supplied by the ventilation device Oxygen in 8-12 minutes through the bacteria in the liquid essentially was used up. At this point there is essentially oxygen depletion new waste water liquid was added for the denitration reaction. The sewage liquid was then mixed and their movement continued by means of a mixer drive unit. the average residence time of the wastewater liquid in the reservoir, which was subjected to continuous aerobic decomposition and denitration was estimated about 24 hours. An analysis of the dispensed liquid afterwards in sedimentation and recirculation of about 5% of the solid constituents removed therefrom was evaluated to the effect that more than 90% of the produced in the waste water liquid The proportion of nitrate compounds is eliminated during the process.

In summary, it can be stated that the invention is an effective one Process and system for wastewater treatment available that continuously is feasible and both maximum decomposition of organic components in wastewater appears to be essentially looking for the elimination of potentially harmful substances, are usually discharged into bodies of water such as streams, rivers and the like.

In particular, the invention provides a method in which the in directed Movement put sewage aerated for aerobic decomposition and this decomposition is carried out until the oxygen in the liquid is practically exhausted is whereupon additional wastewater is added to the already aerated Liquid to denitrate and finally the aerated, denitrated liquid is diverted for clarification and / or sedimentation and / or sludge is returned. The device according to the invention has a ventilation reservoir with inlet and Outlet and between these arranged drive device for continuously flowing Movement of the liquid on, the distances between the individual bodies being longitudinal the flow path, especially the inlet, for maximum aerobic decomposition and Denitration are chosen.

Patent claim /

Claims (3)

Patent or protection claims b Process for continuous wastewater treatment using activated mud, characterized by the features that raw sewage liquid in a self-contained, horizontal circulation path It is introduced that the liquid in this way produces aerobic decomposition as well as formation of nitrogen components is aerated, the aerated liquid covers a first distance along this path, in which the decomposition to practical to exhaust the oxygen content at the point of introduction of raw wastewater continued that thereupon the circulation of the nitrogen compound containing Liquid and raw sewage continues along the path for a second distance, in denetration progresses until the liquid reaches the next vent Reached along the track, the continuously treated liquid for clarification and withdrawing sludge contained therein at a rate which approximates settling corresponds to the injection or supply rate of raw sewage liquid, and that the resulting clarified liquid yield discharged and at least part of the deposited sludge is added back to the liquid in the reservoir, whereby the second route is at least about 10% of the sum of the first and second route. 20 device for performing the method according to claim 1, with a wastewater-absorbing reservoir, which is not indicated, that in the reservoir (10) by conducting means (14) one in itself closed, horizontal Flow path is provided, along which a feed device (12) and a Ventilation drive device (24) is located, the distance between the feed device (12) to 2 and the ventilation drive device (24) seen in the direction of flow at least about 1 o, b the distance between feeding device and ventilation drive device plus - again seen in the direction of flow - the distance between the ventilation device and feed device, and that further the reservoir (10) with a sedimentation system (30) is in communication via an outlet (26). 3. Apparatus according to claim 2, since d u r c h g e k e n n z e i c h n e t that the sedimentation system (30) next to outlets for clarified water and Mud has a return line (34) to the interior of the reservoir (10). Blank page